JPH10122365A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston for an internal combustion engine wherein friction can be reduced while seizure can be prevented. SOLUTION: In a piston 1, a ring land part 3 in a side of a crown surface part 2 and a skirt part 4 continued to this ring land part 3 are provided. A piston pin hole 8 is formed to appear in this skirt part 4. An oval amount in the skirt part 4 of the piston 1, in a side near the ring land part 3 from a plane including an axial line X1 of the piston pin hole 8, is formed smaller than in a side distant from the ring land part 3. Partly in the periphery of the skirt part 4 in a side near the ring land part 3 from the plane including the axial line X1 of the piston pin hole 8 in this small oval amount, a recessed part 10 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine, and more particularly to a piston capable of preventing seizure and reducing friction.

[0002]

2. Description of the Related Art In a piston for an internal combustion engine, when the engine is operated at a high speed and a high load and the side force on the piston is large, there is a concern that seizure may occur between the piston and the inner surface of the cylinder. When the engine is operated at low speed and low load, and the side force on the piston is small, the magnitude of the friction affects the operation performance of the engine.

[0003] Thus, for example, US Patent No. 4,648,309.
In the specification, the oval amount of the skirt portion of the piston,
A piston is disclosed that is enlarged near the plane including the axis of the piston pin hole and smaller than the rest in the rest. The piston, while increasing the oval amount in the trunk near the plane including the axis of the piston pin hole and reducing the contact area with the cylinder inner surface to reduce friction, while reducing the oval amount in the remaining portion It is made smaller to increase the contact area and improve seizure resistance.

[0004]

However, in the prior art, the oval amount is large at the body near the plane contacting the plane including the axis of the piston pin hole, so that the friction can be reduced. In this case, since the oval amount is reduced, in this region, the seizure resistance can be improved, but the reduction of friction may be difficult.

The present invention has been devised in view of such conventional circumstances, and has as its object to provide a piston for an internal combustion engine capable of preventing seizure and reducing friction. I do.

[0006]

The invention according to claim 1 includes a ring land portion on the crown surface side and a skirt portion following the ring land portion, and a piston pin hole is formed facing the skirt portion. In the piston for an internal combustion engine, the oval amount of the skirt portion of the piston is formed smaller on the side closer to the ring land portion than the plane including the axis of the piston pin hole than on the side farther from the ring land portion. A concave portion is formed in a part of the outer periphery of the skirt portion on the side closer to the ring land portion than the plane including the axis of the piston pin hole, which has a small oval amount.

Further, the invention according to claim 2 has a structure in which, in the structure of the invention according to claim 1, the axis of the piston pin hole is offset to the thrust side with respect to the axis of the piston.

According to a third aspect of the present invention, in the first aspect of the present invention, the axis of the piston pin hole is offset from the axis of the piston in a direction opposite to the thrust, so that the piston has a thrust side. In the above, the oval amount of the skirt portion is formed smaller on the side closer to the ring land portion than on the plane including the axis of the piston pin hole than on the side farther from the ring land portion, and the oval amount is small. A recess is formed in a part of the outer periphery of the skirt closer to the ring land than the plane including the axis.

According to a fourth aspect of the present invention, in the configuration of the first to third aspects of the present invention, the dimension of the skirt portion in the axial direction of the piston pin hole is set to a plane including the axis of the piston pin hole. It is configured to be larger on the side closer to the ring land than on the side farther from the ring land.

According to a fifth aspect of the present invention, in the configuration of the second or third aspect of the present invention, on the thrust side of the piston, the size of the skirt portion in the axial direction of the piston pin hole is set to the same value as the piston pin. The configuration is such that the side closer to the ring land than the plane including the axis of the hole is larger than the side farther from the ring land.

According to the present invention, the engine is operated at a medium to low speed.
When operating at low load and the side force on the piston is small, the increase in the contact area between the skirt of the piston and the inner surface of the cylinder is limited by the recess, so the increase in friction at the time of contact with the inner surface of the cylinder is reduced. Can be suppressed. That is, since the oval amount of the piston is formed smaller on the side closer to the ring land portion than on the plane including the axis of the piston pin hole than on the side farther from the ring land portion, the contact area with the inner surface of the cylinder increases. However, since the oval amount is small and a recess is formed in a part of the outer periphery of the skirt portion closer to the ring land portion than the plane including the axis of the piston pin hole, the increase in the contact area is limited. ,
It is possible to suppress an increase in friction.

On the other hand, when the engine is operated at high speed and high load and the side force on the piston is large,
The skirt portion of the piston is elastically deformed. For this reason, the recess formed in a part of the outer periphery of the skirt portion of the piston also contacts the inner peripheral surface of the cylinder. As a result, although the concave portion is formed in the skirt portion, the contact area substantially increases, and the seizure resistance can be improved.

Further, the recess formed in the skirt portion functions as a passage for introducing lubricating oil (engine oil), and advantageously acts to form an oil film on the contact surface with the inner surface of the cylinder.

In particular, according to the present invention, the deformation of the skirt portion when the side force is large is facilitated, and the seizure resistance is advantageously improved.

Accordingly, a piston for an internal combustion engine that can prevent seizure and reduce friction can be obtained.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a plan view of a piston for an internal combustion engine showing an embodiment of the present invention.
1 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is a sectional view taken along line BB of FIG. The internal combustion engine piston indicated by reference numeral 1 in the figure includes a top crown 2 in FIG. 1, a ring land 3 following the crown 2, and a skirt 4 following the ring land 3. I have. The ring land portion 3 has three piston ring grooves 5 in this embodiment.
Is formed.

Reference numeral 6 denotes a pin boss formed on the inner peripheral side of the skirt 4. The pin boss 6 is connected to the skirt 4 via an apron 7, and the axis of the piston 1 (axial center line). ) It is formed to face both sides of Y1.

The pin boss portion 6 is formed with a piston pin hole 8 facing the skirt portion 4. The piston pin hole 8 has its axis (axial line) X1 with respect to the axis Y1 of the piston 1. Are formed so as to be substantially perpendicular. The axis X1 of the piston pin hole 8 is shown in FIGS.
As shown in (1), the piston 1 is offset on the anti-thrust side with respect to the axis Y1. In FIG. 2, X2 is a line passing through the axis Y1 of the piston 1 and parallel to the axis X1 of the piston pin hole 8. In FIG. 3, Y2 is a line passing through the axis X1 of the piston pin hole 8 and parallel to the axis Y1 of the piston 1, and X3 is passing through the axis X1 of the piston pin hole 8 and orthogonal to the axis Y1 of the piston 1. It is a line to do.

The oval amount of the skirt portion 4 of the piston 1 is at least on the thrust side of the piston 1 and on the side closer to the ring land portion 3 than the plane including the axis X1 of the piston pin hole 8 and farther from the ring land portion 3. It is formed smaller. Therefore, the piston 1
The shape of the contact surface 9 when it slides on the inner periphery of the cylinder (not shown) is closer to the ring land portion 3 than the plane including the axis X1 of the piston pin hole 8 as shown by a mesh pattern in FIG. The side has a shape that is wider in the circumferential direction than the side far from the ring land portion 3.

The dimension of the skirt portion 4 in the direction of the axis X1 of the piston pin hole 8 is set such that the side closer to the ring land portion 3 than the plane including the axis X1 of the piston pin hole 8 is farther from the ring land portion 3. Is also formed large. That is, the dimension W2 of the skirt portion 4 on the side closer to the ring land portion 3 than the plane including the axis X1 of the piston pin hole 8 is farther from the ring land portion 3 than the plane including the axis X1 of the piston pin hole 8. (See FIG. 1 and FIG. 2).

As shown in FIG. 2, the dimension W2 of the skirt portion 4 is increased only in the dimension W2 on the thrust side of the piston 1 and remains the dimension W1 on the opposite thrust side, as shown in FIG. This is based on the result of the analysis of the behavior of the piston 1 in the cylinder, whereby the skirt 4 on both the thrust side and the anti-thrust side is obtained.
The weight of the piston 1 can be reduced as compared with the case where the size of the piston 1 is increased. In addition, the expansion of the dimension W2 of the skirt portion 4 can facilitate the deformation of the skirt portion 4 on the thrust side. As described later, when the engine is operated at high speed and high load and the side force is large, It can advantageously contribute to improvement of seizure resistance.

A recess 10 is formed in a part of the outer periphery of the skirt 4 closer to the ring land 3 than the plane including the axis X1 of the piston pin hole 8. This recess 10
As shown in FIGS. 1, 4 and 5, is formed with a predetermined width dimension w and a predetermined depth dimension t, and is formed in a shape open to the ring land portion 3 side. The recess 1
The corner 10a on the bottom side of 0 and the portion 10b where the recess 10 is connected to the body of the piston 1 are formed in an arc shape.

According to such a configuration, the piston 1 operates by being incorporated into an engine (not shown).

At this time, the engine (not shown) operates at medium to low speed.
When the cylinder is operated at a low load and the side force on the piston 1 is small, the contact area between the skirt portion 4 of the piston 1 and the inner surface of the cylinder is limited to be increased by the concave portion 10. Can be suppressed from increasing. That is, the oval amount of the piston 1 is equal to the axis X1 of the piston pin hole 8.
Is formed smaller on the side closer to the ring land portion 3 than on the side including the ring land portion 3, so that the contact area with the inner surface of the cylinder is increased. Since the recess 10 is formed in a part of the outer periphery of the skirt portion 4 closer to the ring land portion 3 than the plane including the axis X1 of the hole 8, an increase in the contact area is limited, and thus an increase in friction is suppressed. You can do it.

On the other hand, when the engine is operated at high speed and high load and the side force on the piston 1 is large, the skirt portion 4 of the piston 1 is elastically deformed. For this reason, the recess 10 formed in a part of the outer periphery of the skirt portion 4 of the piston 1 also contacts the inner peripheral surface of the cylinder.
As a result, although the concave portion 10 is formed in the skirt portion 4, the contact area substantially increases,
Seizure resistance can be improved.

Also, the concave portion 1 formed in the skirt portion 4
Numeral 0 functions as a passage for introducing lubricating oil (engine oil), which advantageously acts on the formation of an oil film on the contact surface with the inner surface of the cylinder (not shown).

Therefore, the piston 1 for an internal combustion engine that can prevent seizure and reduce friction can be obtained.

FIGS. 6 to 8 show another embodiment of the present invention. The first embodiment differs from the first embodiment in that, in the embodiment shown in FIG. 6, the dimension of the skirt portion 4 in the direction of the axis X1 of the piston pin hole 8 is changed to the axis X1 of the piston pin hole 8. This is a point that the dimension on the thrust side and the opposite thrust side of the piston 1 is the same without being larger on the side closer to the ring land portion 3 than on the side including the ring land portion 3 than on the far side.

The embodiment shown in FIG. 7 is characterized in that the recess 10 formed in a part of the outer periphery of the skirt portion 4 is formed in a shape whose width dimension increases toward the ring land portion 3 side. is there.

In the embodiment shown in FIG. 8, the concave portion 10 formed in a part of the outer periphery of the skirt portion 4 is formed so that the ring land portion 3 is larger than the plane including the axis X1 of the piston pin hole 8.
Is extended to the side far from the ring land portion 3 as well as to the side close to the ring land 3.

In each embodiment, since the other structure is the same as that of the above-described embodiment, the same components are denoted by the same reference numerals, and overlapping description will be omitted.

With such a configuration, the same operation and effect as those of the above embodiment can be obtained. In addition, in the embodiment shown in FIG. 8, the contact area with the cylinder is reduced even on the side far from the ring land portion 3, so that the friction can be further reduced.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to this embodiment, and can be changed without departing from the spirit of the invention.
For example, the concave portion 10 formed in a part of the outer periphery of the skirt portion 4 may have a shape that is not released to the ring land 3 side.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result, the width w of the recess 10 formed in a part of the outer periphery of the skirt 4 is set to about 1/5 of the dimension W1 of the skirt 4, and the depth t is set to about 20 μm. Results were obtained.

[0036]

As described in detail above, according to the present invention, it is possible to obtain a piston for an internal combustion engine capable of preventing seizure and reducing friction.

[Brief description of the drawings]

FIG. 1 is a plan view of a piston for an internal combustion engine showing an embodiment of the present invention, viewed from a thrust side.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a sectional view taken along line CC of FIG. 1;

FIG. 5 is an enlarged view showing a portion D in FIG. 3;

FIG. 6 is a view similar to FIG. 1, showing another embodiment of the present invention.

FIG. 7 is a drawing similar to FIG. 1, showing another embodiment of the present invention.

FIG. 8 is a view similar to FIG. 1, showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston 2 Crown surface part 3 Ring land part 4 Skirt part 5 Piston ring groove 8 Piston pin hole 10 Concave part X1 Axis line of piston pin hole Y1 Axis line of piston

Claims (5)

[Claims] 1. A piston for an internal combustion engine, comprising: a ring land portion on a crown surface side; and a skirt portion following the ring land portion, wherein a piston pin hole is formed facing the skirt portion. Is formed smaller on the side closer to the ring land than on the plane containing the axis of the piston pin hole than on the side farther from the ring land, and the plane containing the axis of the piston pin hole is smaller in this oval. A piston for an internal combustion engine, characterized in that a recess is formed in a part of the outer periphery of the skirt portion closer to the ring land portion. 2. The piston for an internal combustion engine according to claim 1, wherein an axis of said piston pin hole is offset to an opposite thrust side with respect to an axis of said piston. 3. An axial line of the piston pin hole is offset to an opposite thrust side with respect to an axis of the piston, and an oval amount of the skirt portion on the thrust side of the piston is smaller than a plane including an axis of the piston pin hole. The skirt portion is formed smaller on the side closer to the ring land portion than on the side farther from the ring land portion, and has a smaller oval amount, and has a smaller outer circumference of the skirt portion on the side closer to the ring land portion than the plane including the axis of the piston pin hole. The piston for an internal combustion engine according to claim 1, wherein a concave portion is formed in the portion. 4. The size of the skirt portion in the axial direction of the piston pin hole is formed larger on a side closer to the ring land portion than a plane including the axis of the piston pin hole than on a side farther from the ring land portion. The piston for an internal combustion engine according to any one of claims 1 to 3, characterized in that: 5. On the thrust side of the piston, the dimension of the skirt in the axial direction of the piston pin hole is
4. The piston for an internal combustion engine according to claim 2, wherein the piston is formed larger on a side closer to the ring land portion than a plane including the axis of the piston pin hole than on a side farther from the ring land portion.